xsl fo - FOP trimming spaces and tabs inside strings -

i'm using fop libraries v1.1 produce pdf, , noted fop default collapse white-spaces inside strings. example block like:

<fo:block>   sample                   text </fo:block> 

render as

sample text 

eliminating whitespaces. keep strings inner whitespaces in generated pdf, tried use white-space="pre" attribute inside block tag, preserves white-spaces outside string.

then tried use white-space-treatment="preserve" attribute inside block tag, rendered page had collapsed white-spaces.

finally tried use white-space-collapse="false" attribute inside block, , in case rendered page had collapsed white-spaces.

why fop collapsing default white-spaces inside strings? there way change fop behaviour in order preserve white-spaces inside strings?

white-space="pre" should work here or may use linefeed-treatment = "preserve", white-space-collapse = "false", white-space-treatment = "preserve", wrap-option = "no-wrap" equal white-space="pre". more information may visit http://www.learn-xsl-fo-tutorial.com/blocks-inlines.cfm#h1.6